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.\"	$OpenBSD: startuphook_establish.9,v 1.3 2003/03/06 04:03:40 david Exp $
.\"
.\" Copyright (c) 1995 Niklas Hallqvist.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\"
.Dd July 27, 2001
.Dt STARTUPHOOK_ESTABLISH 9
.Os
.Sh NAME
.Nm startuphook_establish ,
.Nm startuphook_disestablish
.Nd add or remove a startup hook
.Sh SYNOPSIS
.Ft void *
.Fn startuphook_establish "void (*fn)(void *)" "void *arg"
.Ft void
.Fn startuphook_disestablish "void *cookie"
.Sh DESCRIPTION
The
.Fn startuphook_establish
function adds
.Fa fn
to the list of hooks invoked by
.Xr dostartuphooks 9
at startup.
When invoked, the hook function
.Fa fn
will be passed
.Fa arg
as its only argument.
.Pp
The
.Fn startuphook_disestablish
function removes the hook described by the opaque pointer
.Fa cookie
from the list of hooks to be invoked at startup.
If
.Fa cookie
is invalid, the result of
.Fn startuphook_disestablish
is undefined.
.Pp
Startup hooks should be used to perform one-time activities
that must happen immediately before the root and swap devices
are configured, but after normal device autoconfiguration.
.Pp
Startup hooks are, like shutdown hooks, implemented via the more general
.Xr dohooks 9
API.
.Sh RETURN VALUES
If successful,
.Fn startuphook_establish
returns an opaque pointer describing the newly established
startup hook.
Otherwise, it returns
.Dv NULL .
.Sh EXAMPLES
It may be appropriate to use a startup hook to provide potential root or
swap devices that have delayed configuration.
The
.Xr iop 4
shows an example of this usage.
.Sh SEE ALSO
.Xr dohooks 9 ,
.Xr doshutdownhooks 9 ,
.Xr dostartuphooks 9
.Sh BUGS
The names are clumsy, at best.